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The Codebreakers of Bletchley Park

My interest in the work of the codebreakers of Bletchley Park stems from my own role working on enciphered Warsaw Pact messages during the Cold War. I wrote my first book on codebreaking in the late 1990s. Station X accompanied a Channel 4 television series on Bletchley Park and went on to become a number one bestseller, staying at the top of the Sunday Times bestseller list for weeks. I am a member of the board of the Bletchley Park Trust and the Chair of the team of experts who advise the board on the history of
Bletchley Park.

Britain’s codebreakers arrive at Bletchley Park, their wartime home, in August 1939.

The Secrets of Station X

I have since written several more books on the wartime codebreakers, including The Secrets of Station X which I’m very proud to say is frequently described as the definitive history of Bletchley Park.

Deliberately written in a very accessible way, it tells the story of Bletchley Park from its earliest beginnings right up to the end of the war, concentrating on the people themselves, the groundbreaking work they carried out and the precise impact it had on the war.

The codebreakers’ efforts helped to win the war against the U-Boats in the Atlantic, against Rommel in North Africa, against the Japanese in the Far East and perhaps most importantly against the German forces at D-Day and during the invasion of Europe. Along the way, they made great strides in developing modern technology, most notably Colossus, the world’s first digital electronic computer.

Colossus, the world’s first electronic digital computer, built to help break teleprinter messages between Hitler and his generals.

The Emperor’s Codes

While Bletchley Park’s astonishing efforts to break German ciphers and codes has become much better known, not least due to the TV programme The Bletchley Circle and the film The Imitation Game, very few people realise that a large part of the work at Bletchley was carried out on Japanese codes. This led me to write The Emperor's Codes: Bletchley Park and the Breaking of Japan's Secret Ciphers.

At the time, it was the accepted wisdom that American codebreakers broke the bulk of the Japanese codes and ciphers. But The Emperor's Codes drew on files newly released to the Public Record Office to show that in fact most were originally broken by British codebreakers but the Americans were far better at keeping on top of the codes due to their superior technological capability.

The Bletchley Park Codebreakers

I owe a great debt of thanks in my research on Bletchley Park to the work and knowledge of Ralph Erskine, a retired lawyer who is one of the leading experts on cryptography during the Second World War. This led to our collaboration in another book Action This Day, now republished as The Bletchley Park Codebreakers.

It’s a collection of essays including chapters by a number of former codebreakers and leading British and American historians on the work of the British codebreakers. They include codebreaker Hugh Foss describing how he had originally broken the German Enigma machine cipher during the 1920s while testing it to see whether it was suitable for use by the British military and embassies abroad. He rejected it as being too easy to unravel!

Other contributors include Edward Simpson, who led Bletchley’s work on breaking the main Japanese naval code JN25, and Shaun Wylie on Colossus, the world's first digital electronic computer, which was conceived by Max Newman, Donald Michie and Jack Good on the basis of the ideas of Alan Turing, perhaps the most famous of the British codebreakers, and built by Post Office engineer Tommy Flowers.

All royalties from The Bletchley Park Codebreakers go to the Bletchley Park Trust.

A German army three-rotor Enigma machine

The Debs of Bletchley Park

One of the most interesting aspects of the work at Bletchley was the involvement of so many women. At the end of the war, there were 10,471 people at Bletchley and its main outstations of whom 7,000 (two-thirds) were women. It is frequently suggested that all of these women were “tiny cogs in a huge machine” doing very mundane work. That is very far from the truth.

Clearly, with men needed to fight on the frontline, many of the most basic jobs were carried out by women, but equally many of the top codebreakers, Mavis Batey, Margaret Rock and Joan Clarke, to name just a few, were women. Batey made the initial breaks into three different machine ciphers. Turing broke only one. That’s a simplistic point, but one well worth making.

So when I was asked to write a book about the women at Bletchley, I jumped at the chance. The book was called The Debs of Bletchley Park and Other Stories. The publishers insisted on the first half of that title. I insisted on the other half, to make clear that the women weren’t just Debs, the young women from rich families who came out as Debutantes each summer season in an attempt to ensure they met rich young men from similarly posh families.

The Bletchley women included a large number from ordinary working-class families and represented every section of society. They enlivened Bletchley Park with their ideas, with their energy and with Bletchley packed jam full of young men and women, there were an awful lot of romantic encounters. But the overwhelming memory of Bletchley for many of the young women there was the way in which they were treated as equals by everyone from university professors to military officers.

Mavis Batey summed it up: “Women who worked at Bletchley Park have much to be grateful for,” she told me. “It was a remarkable community where neither rank nor status counted, and a girl of 19 with a bright idea would be encouraged to take it forward, long before any official equality for women.”